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@@ -97,6 +97,24 @@ Instructions: Please answer the following questions in complete sentences. Your
     [source][wiki-von-neumann]
 
 1. What role do device controllers and device drivers play in a computer system?
+
+    Each device controller is in charge of a specific type of device.
+    The device controller is responsible for moving the data between the peripheral
+    devices that it controls and its local buffer storage.
+    Operating systems have a device driver for each device controller. This
+    device driver understands the device controller and presents a uniform
+    interface to the device to the rest of the operating system.
+
+    To start an I/O operation, the device driver loads the appropriate registers
+    within the device controller. The device controller, in turn, examines the
+    contents of these registers to determine what action to take. The controller
+    starts the transfer of data from the device to its local buffer. Once
+    the transfer of data is complete, the device controller informs the device
+    driver via an interrupt that it has finished its operation. The device
+    driver then returns control to the operating system, possibly returning
+    the data or a pointer to the data if the operation was a read. For
+    other operations, the device driver returns status information.
+
 1. Why do clustered systems provide what is considered high-availability service?
 1. Describe an operating system’s two modes of operation.
 1. Define cache, and explain cache coherency.